Mill for effecting separation of pith and fiber from stalky vegetable materials



Nov. 12, 1957 P. M. HORTON ETAL 2,812,552

MILL FOR EFFECTING SEPARATION OF PITH AND FIBER FROM STALKY VEGETABLEMATERIALS Filed 001;. 12, 1954 3 Sheets-Sheet 1 B @Wr/M ATTORNEY 1957*P. M. HORTON ET AL 2,812,552

MILL FOR EFFECTING SEPARATION OF PITH AND FIBER FROM STALKY VEGETABLEMATERIALS Filed 001%. 12, 1954 3 Sheets-Sheet 2 Fuzz 090R 022/ 4rikaramaze? Nov. 12, 1957 P. M. HORTON ETAL 2,812,552

MILL FOR EFFECTING SEPARATION OF PITH AND FIBER FROM STALKY VEGETABLEMATERIALS H Filed Oct. 12, 1954 3 Sheets-sheaf 3 Unit 1'5 IVHLL FOREFFECTING SEPARATION OF PITH AND FIBER FROM STALKY VEGETABLE MATE- RIALSApplication October 12, 1954, Serial No. 461,822

7 Claims. (Cl. 19-30) This invention relates to mills for processingfibrous Vegetable materials containing'pith and fiber to separate thepith from the fiber. .More particularly, this invention relates .to ahammer mill for treating stalky fibrous vegetable materials, to separatethem into suitable, pithfree fiber and pith fractions.

The invention of this application is in the nature of animprovement onthe invention disclosed and claimed in Our copending application SerialNo. 103,268, filed July 6, 1949, which issued as Patent No. 2,729,85 8on January 10, 1956, and this application is a continuation-in-part ofsaid copending application. 7

The mills of this invention are designed to treat fibrous vegetablematerials, such as sugar cane bagasse, sorgho bagasse, bamboo, reedcanes, maize stalks and similar products in which the fibrousconstituents are in a resilient condition and are particularly designedto treat fresh bagasse. production of pulp for use in paper oralpha-cellulose production or other purposes, but their commercial usein such fields has been handicapped by the presence of varying amountsof pith. The pith fraction, on the other hand, is suitable foruse as afilter aid, particularly in the clarification of sugar juice, in animalfeeds, agricultural mulches, and as an absorbent in explosivemanufacture. However, in order to effect the separation of the fiberfro-m the pith, so that either'or both of these fractions of thevegetable fibrous materials may be used 7 for any of the above or otherpurposes, it is important that the separation be efiected economically,i. e., at low,

cost, because otherwise neither the fiber nor the pith tates Patent iceof the pith in the stored or aged bagasse is partially destroyed orchanged in nature. Furthermore, the fibrous material in the aged bagasseis less resilient than is the fibrous fraction of fresh bagasse. Whilethe invention herein will be described hereinafter chiefly in connectionwith the processing of fresh bagasse, it will be understood theinvention is not limited thereto.

The fibers of such materials are suitable for the can compete with otheravailable raw materials for these I I and as it first emerges from theconventional milling operation employed in the production of sugar fromsugar cane. Fresh bagasse normally contains about percent by weight ofmoisture, and between 4 and 6 percent of soluble solids, the majorportion of which are sugars. The bagasse is usually heavily infectedwith a wide variety of microflora which attack the soluble materialspresent, including the-sugars, with consequent fermentation and otherreactions which evolve considerable heat when the bagasse is stored inlarge piles. to drive off a considerable amount of the moisture presentin the bagasse and also to raise the temperature of the stored materialto about C. At such temperatures the material is effectively sterilizedand dried, while at the same time, because of the acid products producedby the It is among the objects of the present invention to provide ahammer mill in which the separation of the pith and fiber can beaccomplished simply,'continuously and economically, including low-powerrequirements for driving the mill and effecting the said separation.

Other objects and advantages of our invention will become apparent inconnection with the following descrip tion, and a consideration of theshowing in the accompanying drawings of two embodiments of ourinvention. In these drawings,

' Fig. 1 is anend view of a hammer mill embodying our invention; i I l VFig. 2 ,is a side elevation of the mill shown in Fig. 1;

Fig. 3' is a vertical section through the mill, taken in a planeindicated by the line 3-3 of Fig. 1;

Fig. 4 is a vertical section taken in a plane indicated by the lines 4-4of Figs. 2 and 3; and v Fig. 5 is a vertical section through a modifiedform of hammer mill embodying our invention.

In the embodiment shown in Figs. 1-4 inclusive,-10 indicates a casingconsisting of an uppersection 1.1 and a lower section 12, desirablydetachably secured together as at 13. However, a casing inwhich both thelower and upper sections are made integral and not detachably securedmaybe used if desired. v

An inlet 14.is disposed in an end wall 15 near the top thereof, throughwhich inlet the fresh bagasse may be fed to'the mill continuously, asfor example by a screw conveyor (not shown). Suitably journalled inbearings 16 and 17, disposed contiguous to the end walls15 and18respectively is a rotor shaft 19. This shaft may be driven by a pulley21 arranged to be connected to a. suitable source of power or by anyother suitable drive, such for example as an electric motor connected tothe shaft 19 through suitable reduction gearing (not shown).

Mounted on the shaft 19 is the rotor 22 constituted, in the embodimentof the invention shown, of a plurality of circular plates 23 spacedapart axially and to which beat ers or hammers 24 are secured by bolts25which connect the plates together. The hammers project outwardlybeyond the periphery of the plates as clearly shown in Figs. 3 and 4 andpreferably are arranged in a generally spiral path. In other words, withthe shaft 19,

4 at rest, each fourth hammer may extend up vertically,

This heat is sufiicient micro-organisms, it is subjected to a mild formof acid the next successive hammers of each series of four extendshorizontally in one direction, the next successive hammer of each seriesof four extends downwardly andthe last hammer of each series extendshorizontally in the opposite direction. A suitable number of hammers,for instance, the last four or eight nearest the end wall 18, may havetheir outer ends twisted somewhat towardahelical position in respect tothe axis of the shaft 19, so as to act as pushers to advance thematerial towards'the fiber discharge chute 26 in the diagonally oppositeportion of the casing from that containing inlet 14. The twisted hammersare indicated by the reference numeral The heaters or hammers 24 may betightly secured to plates 23 so that they extend outwardly in a radialdirection. Alternatively they may be looselyv mounted on the bolts 25,so that the latter act as pivotal supports," and the hammers may swingon the bolts and assume ra--v dial positions due to centrifugal force.

In the embodiment of the invention shown in Fig. 3,;

garages:

theharnrners 24 are disposedto extend oven a. portion. of

the fiber discharge chute 26, so as to aid in effecting the discharge ofthe fibrous material from the mill. If desired, however, and as shown inthe modification of Fig;

hereinafter described; the hammers: andthe rotor carryr ing the samemaybe sopositioned-thatno portion of the rotor, including the hammerscarried thereby, is positioned above the discharge chute 26 the lengthof the rotor being co-extensive with that of the semi-cylindrical screen27 disposed directly beneath the rotorand through which thepith isdischarged;

Screen 27 may be suitably supported in the mill, for example, at itsopposite ends and desirably'has a thickness offrom %"'to A" or more. Itisprovided' with perforations of a size to permit: the pith to. passtherethrough and retain the fiber. This screen should be sufficientlydurable and sturdy to withstandthe action of the hammerson the bagassepassing over" the screen, without deformation or damage to the screen;Aperforated steel semi-cylindrical screen having a thickness of at least41, desirably about has been found. satisfactory for use in separatingfresh bagasse into pith and fiber'fractions. Screen 27, as best shown inFig. 4, completely encircles the lower half of the rotor 22 and has itsterminal ends 28 and 29 abutting the ends of the flanges 30 and 31respectively, on the upper section 11 of the casing 10. A pith dischargechute. 3,2. communicates with the underside of the screen. Thisdischarge chute, as best shown in Fig. 3, has its upperportioncoextensive in length with the length of the screen 27. a

In accordance with this invention, the upper section 11 is shaped toprovide three, distinct zones 33, 34 and 35 along the length of themill. Zone 33, at the inlet end of the mill, desirably is of a length(the dimension along the axis of shaft 19) equal to 20 to 35 percent ofthe length of the rotor and of a height to provide a free space abovethe tips of the hammers equal to from 35 to 45 percent of the rotordiameter (the diameter of a circle defined by the tips of the hammerswhen rotating). The cross-sectional area of this free space preferablyis from 50 to 75 percent of the cross-sectional. area of the hammercircle, i. e., the circle defined by the tips of the hammers when theyrotate. Zone 33 thus provides the necessary space in which the freshbaggasse may rotate above the tips of the hammers while being beaten bythe; hammers as the rotor rotates. In other words, rotation of the rotoreffects a beating of the incoming fresh bagasse, causing a mass of itsto rotate in zone 33 abovethehammers. While thus rotating the mass iscontinuously beaten by the hammers. and continuously movedlongitudinally along the length of the rotor as the bagasse iscontinuously fed to themill through the inlet 14, some of the bagasse,probably a minor portion, being removed from the rotating mass, forcedover the screen 27 and returned to the rotating mass. This actioneffects a. loosening of the fibers, without, however, materiallyreducing the length of the fibers, in the bagasse, and ,a separation ofsome of the .pith which drops down onto and through screen 27 from whichit is discharged.

Zone 34, which communicates with zone 33, is defined by the inclined topwall 36 of the casing 10, which wall is at an angle of to 30 to thehorizontal. Thus zone 34 is of gradually diminishing depth from theinlet end of the mill towards the discharge end. The right hand ordischarge end of zone 34 (viewing Fig. 3) is of a depth to. provide asmall clearance 37 above the tip of the ham-. mers, sufficient to permitfree rotation of the hammers and to avoid clogging of the mill but smallenough to insure that all of the bagasse is caused to pass over thescreen 27. Hence, as the bagasse. moves continuously longitudinallythrough the millit is forced more and more into the hammer circle.Accordingly all of the material fed to the mill is effectively beaten bythe hamrners 24 before it reaches the discharge zone 35 communicatingwith zone 34, thus effecting substantially coma plete removal of thepith from the fiber.

As indicated, zone 35 is the discharge zone through which the fiber,after having passed over the screen 27 and having had the pith removedtherefrom, is discharged into, and through fiber discharge chute 26communicating with, zone 35.

Disposed in side wall 38 of upper section 11 of the mill in zones 33 and34 are a series of spaced spray-jets or liquid inlets 39. While foursuch inlets are shown, it will be understood any desired number may beused and these inlets may be positioned on the opposite side walls.Water is sprayed through these inlets in a downward direction, wettingthe bagasse being processed and facilitating the separation of the pithfrom the fiber, i. e., the water has a tendency to wash the pith out offiber masses and clean the screen 27. The water-pith mixture drainsthrough screen 27 and flows into and through the pith discharge chute32. While the use of these sprays is preferred, they are not essential,as satisfactory separation of the pith and fiber may be obtained runningthe mill dry.

The operation of the mill should be clear from the above descriptionthereof. It is noted that the action of the mill is to hackle and hammerthe bagasse, rather than to rub or grind it, this action functioning toloosen and free the fibers from each other, rather than to break themup, and after loosening effected in zone 33 to carry the loosened fibersaround and over the screen 27 to permit maximum opportunity for the pithto separate from the fibers and be removed therefrom by passage throughscreen 27 which retains the fibers. This action of freeing the pith fromthe fibers is facilitated by the sprays of water supplied to the millthrough the jets or inlets 39.

In the modification of Fig. 5, in which like parts have been given likereference numerals, the casing or housing of the mill is provided with atop central inlet 41 through which the bagasse is fed continuously tothe mill by any suitable feeding equipment such as a screw conveyor,etc. Disposed directly beneath inlet 41 is the central zone 42 which ingeneral corresponds in dimensions and functions to zone 33 of themodification of Figs. l-A inclusive. In zone 42a mass of the incomingbagasse rotates in the free space above the tips of the hammers, whichfree space is of a depth or height desirably equal to from 35-45 percentof the rotor diameter while being hackled by the 1'97. tating hammers.Leading from opposite sides of the free space 42. are the zones 43 and44 respectively of gradual ly diminishing depth, and which correspond ingeneral, in structure, and function to free space 34 of the modificationof Figs. 1-4 inclusive. The free spaces 43 and 4.4 are defined by theinclinedtop walls 45 and 46 respectively, of the housing, which wallsmay be at an angle of from l530. to the horizontal. Zones 43 and 44communicate respectively with discharge zones 47 and 48 from which leadthe fiber discharge chutes 49 and 51 respectively. A pith dischargechute 52, Communicates with the underside of screen 27.

The side walls of the casing, defining zones 43 and 44 of the mill ofFig. 5,, may be provided with jets or liquid inlets corresponding toinlets 39.

In the operation of the apparatus of Fig. 5, fresh bagasse is suppliedcontinuously to the mill through inlet 41, accumulates and forms arotating mass above the tips of the hammers, which mass. is beaten bythehammers 24 as they rotate. The action of the hammers and thecontinuous supply of bagasse to the inlet 41 causes the bagasse to movefrom. zone, 42 in opposite direction into and through zones 43 and 44,where the beating action is continued and the loosened bagasse caused tomove over the screen 27 while being beaten by the hammers. To facilitatesuch movement, if desired, one or more series oftthe hammers in zone 42.may be twisted, with some of the hammers twisted in a direction to causethe material to move through zone 43 and others in a direction to causethe material to move through zone 44. All of the material thus suppliedto the mill is hackled and beaten to effectively separate the pith fromthe fiber, the pith flowing continuously through the openings in screen27 and being discharged from the mill through pith discharge chute 52,and the pith-free fiber flowing continuously through the fiber dischargechutes 49 and 51 at opposite endsof the mill.

The mills hereinabove described are inexpensive to manufacture andoperate, the power consumption is unusually low and substantiallycomplete separation of the pith from the fiber is effected.

Since certain changes may be made in the mills hereinabove described,and different embodiments of the invention could be made withoutdeparting from the scope thereof, it is intended that all mattercontained in the above description, or shown in the accompanyingdrawings, shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:

1. Hammer mill apparatus for processing crushed fibrous stalkscontaining pith to separate the pith and the fibers, said apparatusincluding a longitudinally extending casing having an inlet in the upperpart thereof for said crushed stalks, a rotating shaft in said casing,extending lengthwise thereof, hammers carried by said shaft for breakingup said crushed stalks and liberating the pith therein, a substantiallysemi-cylindrical screen below said shaft and substantially concentrictherewith, a pith discharge chute directly beneath said screen, throughwhich the pith liberated from said fibrous stalks is discharged, theupper part of said casing at the inlet portion thereof being shaped toprovide a relatively large free space directly above some of saidhammers and extending in the same longitudinal direction as thedirection of feed of the crushed stalks through said casing, in whichlarge free space a mass of the crushed stalks fed to the machine may berotated while subjected to repeated beating by said hammers, said largefree space merging into a free space disposed above other of saidrotating hammers, which second mentioned free space is of graduallydiminishing depth, so that the crushed stalks passing therethrough areforced into contact with the rotating hammers and are carried therebyover said screen to effect removal of the pith from the fibers, theportions of said casing defining said free spaces having imperforateside walls which merge into the side Walls of said semi-cylindricalscreen forming substantially smooth and continuous surfaces free ofprojections on the opposite sides of said rotating hammers, and adischarge passageway for the fibers at the terminal end of said secondmentioned free space leading from the base of said casing.

2. Hammer mill apparatus as defined in claim 1, in which the saidfirst-mentioned free space is from 35 to 45 percent of the diameter ofthe circle defining the path through which said hammers rotate, the topof the secondmentioned free space is inclined at an angle of from 15- 30to the longitudinal axis of said rotating shaft carrying said hammersand the cross-sectional area of the first mentioned free space is withinthe range of 50-75 percent of the cross-sectional area of the beatercircle.

3. Hammer mill apparatus as defined in claim 1, in which a side of thecasing defining the firstand secondmentioned free spaces is providedwith spaced inlets for supplying liquid.

4. Hammer mill apparatus for processing crushed fibrous stalkscontaining pith to separate the pith and the fibers, said apparatusincluding a casing having an inlet in the upper part thereof for saidcrushed stalks, a shaft in said casing, extending lengthwise thereof,hammers carried by said shaft for breaking up said crushed stalks andliberating the pith therein, a substantially semi-cylindrical screenbelow said shaft and substantially concentric therewith, a pithdischarge chute directly beneath said screen, through which the pithliberated from said crushed stalks is'discharged, the upper part of saidcasing being shaped to provide, in the order mentioned starting with theinlet and thereof, (1) a relatively large free space directly above someof said hammers and extending in the same longitudinal direction as thedirection of feed of the crushed stalks through said casing, in whichlarge free space the crushed stalks fed to the machine may be rotatedWhile subjected to repeated beating by said hammers, (2) a free space ofgradually diminishing depth, communicating with the first-mentioned freespace, disposed above other of said hammers and shaped to cause thecrushed stalks passing therethrough to move down into contact with therotating hammers and to be carried thereby over said screen to effectremoval of the pith from the fibers, and (3) a fiber discharge zonecommunicating with said second-mentioned free space, the portions ofsaid casing defining said free spaces having imperforate side wallswhich merge into the side Walls of said semicylindrical screen formingsubstantially smooth and continuous surfaces free of projections on theopposite sides of said rotating hammers, and a fiber discharge chutecommunicating with the base of said discharge zone.

5. Hammer mill apparatus for processing crushed fibrous stalkscontaining pith to separate the pith and the fibers, said apparatusincluding a longitudinally extending casing having near the top of oneend wall an inlet for said crushed stalks, a horizontally extendingshaft in said casing, extending lengthwise thereof, hammers carried bysaid shaft for breaking up said material and liberating the piththerein, a substantially semi-cylindrical screen below said shaft andsubstantially concentric therewith, said screen being of a length lessthan that of the length of said casing and extending from one end ofsaid casing short of the other end, a pith discharge chute directlybeneath said screen through which pith liberated from said fibrousstalks is discharged, a chute for the discharge of fibrous materialdisposed at the base of the casing, contiguous to one end of saidscreen, the upper part of said casing at the inlet end thereof beingshaped to provide a relatively large free space directly above some ofsaid hammers, and extending in the same longitudinal direction as thedirection of feed of the stalks through said casing, in which large freespace the crushed stalks fed to the machine may be rotated whilesubjected to repeated beating by said hammers, said large free spacemerging into a free space disposed above other of said rotating hammers,which second-mentioned free space is of gradually diminishing depth sothat the crushed stalks passed therethrough are forced into contact withthe rotating hammers and are carried thereby over said screen to effectremoval of the pith from the fiber, the portions of said casing definingsaid free spaces having imperforate side Walls which merge into the sidewalls of said semi-cylindrical screen forming substantially smooth andcontinuous surfaces free of projections on the opposite sides of saidrotating hammers.

6. A hammer mill comprising a longitudinally extending casing, asemi-cylindrical screen disposed in said casing, spaced from theopposite ends of said casing, discharge chutes leading from the base ofthe said casing beyond the ends of said screen for the discharge offibrous material substantially free of pith, a pith discharge chutedirectly beneath said screen, a longitudinally extending rotatable shafthaving a rotor thereon equipped with hammers, which rotor is of a lengthto extend over the screen, said casing having a substantially centrallylocated top inlet for supplying the fibrous stalks to the casing andbeing shaped to provide a free space of substantial depth disposeddirectly above the tips of some of said hammers,

in which space a mass of stalks fed to the machine through said inletmay be rotated while being beaten by said hammers, said casing beingalso shaped to provide zones of gradually diminishing depth extendingfrom said free space towards the ends of said casing and communicatingstalks fed to the machine are moved in opposite directions,

away from each other so that they are gradually brought into contactwith other of said rotating hammers, and carried thereby over saidscreens to effect removal of the pith from the fiber, the fiber thusseparated from the pith being discharged through said fiber dischargechutes and the pith through said pith discharge chute.

7 A hammer mill comprising a longitudinally extending casing, a topcentrally disposed feed inlet to said casing, a semi-cylindrical screendisposed in said casing, spaced from the opposite ends of said casing,discharge chutes leading from the base of the said casing beyond,

the ends of said screen for, the discharge of fibrous material,substantially free of pith, a discharge chute directly beneath saidscreen for the discharge of pith, a longim tudinally extending rotatableshaft having a rotorthereon equippedwith hammers, which rotor is of alength to extend over the screen, the top of, said casing being shapedto provide, (1) a free space of substantialdepth disposed directly abovethe tips of some of said hammers and communicating with said inlet, inwhich free space a mass of stalks fed to the machine may be rotatedwhile being beaten by said hammers, (2) zones of gradually diminishingdepthextending from said free space towards the ends of said casing,through-which zonescrushed stalks fed to the machine are moved inopposite directions away from each other so that they are graduallybrought into conmet with other of said rotating hammers, and carriedthereby, yer said screens to effect removal of the pith from the fiber,and (3) fiber discharge zones communicating with said zones of graduallydiminishing depth.

, References Cited in the file of this patent UNITED STATES PATENTS28,361 Gilmore 2.. May 22, 1860 148,997 Taylor Mar. 24, 1874 911,335Sargent Feb. 2, 1909 978,237 Treese Dec. 13, 1910 1,990,992 Lang et alFeb. 12, 1935

